assert_function {assertions}

Assert input is a function

Description

Assert input is a function

Usage

assert_function(x, msg = NULL, call = rlang::caller_env(), arg_name = NULL)

Arguments

x

An object

msg

A character string containing the error message to display if x is not a function

call

Only relevant when pooling assertions into multi-assertion helper functions. See cli_abort for details.

arg_name

Advanced use only. Name of the argument passed (default: NULL, will automatically extract arg_name).

Value

invisible(TRUE) if x is a function, otherwise aborts with the error message specified by msg

Examples

try({
# Assert that a variable is a function
x <- function(a, b) { a + b }
assert_function(x)  # does nothing

# Assert that a variable is not a function
x <- "not a function"
assert_function(x)  # stops execution and prints an error message
})